1. Field of the Invention
The present invention relates to a semiconductor nonvolatile memory device and a method for production of the same, more particularly relates to an OTP (one time programmable) semiconductor nonvolatile memory device capable of being written with data only one time and a method for production of the same.
2. Description of the Related Art
As nonvolatile semiconductor memory devices, floating gate type, MNOS type, MONOS type, and other flash memories having various characteristics and capable of erasing data together have been developed. They have CMOS transistors as decoders and other peripheral transistors of memory cell arrays.
However, a flash memory has had a problem in that about 20 to 30 masks were necessary for producing the same, so the manufacturing cost was high.
On the other hand, as a read only memory device capable of being written with data only one time (OTPROM (read only memory)), a memory cell having one transistor and one oxide film fuse has been developed. This is disclosed in for example Japanese Examined Patent Publication (Kokoku) No. 4-9388, Japanese Examined Patent Publication (Kokoku) No. 58-28750, or Japanese Examined Patent Publication (Kokoku) No. 63-22073.
For example, Japanese Examined Patent Publication (Kokoku) No. 4-9388 discloses a memory cell having a structure shown in FIG. 1.
For example, a gate electrode 104 is formed on a channel forming region 102 of a p-type semiconductor substrate 101 via a gate insulating film 103, and a source region 105 and a drain region 106 containing n-type impurities are formed in the semiconductor substrate 101 on the two sides thereof, whereby a MOS field-effect transistor is formed.
An insulating film 110 of silicon oxide is formed covering the MOS transistor, contact holes reaching the gate electrode 104, source region 105, and the drain region 106 are formed, and a gate interconnection 115, source interconnection 116, and a drain interconnection 117 made of for example aluminum are filled in the contact holes.
Here, a silicon oxide film 114 is formed at an interface between the source region 105 and the drain interconnection 116 and insulates the two.
In a memory cell having the above structure, by applying a high voltage between the source region 105 and the source interconnection 116 according to the data to be written, the insulation in the silicon oxide film 114 is broken and the source region 105 and the source interconnection 116 are made conductive. Thus, data can be stored by conduction or nonconduction between the source region 105 and the source interconnection 116 in each memory cell.
Also, Japanese Examined Patent Publication (Kokoku) No. 58-28750 and Japanese Examined Patent Publication (Kokoku) No. 63-22073 disclose memory cells having structures shown in FIG. 2 and FIG. 3 are disclosed.
These are substantially the same as the memory cell having the structure shown in FIG. 1, but a polysilicon layer 120 is formed connected to the source region 105, and the source interconnection 116 is formed at an upper layer thereof via the silicon oxide film 114.
Also, in FIG. 2, the polysilicon layer 120 is formed also in the drain region 106, and the drain interconnection 117 is formed at an upper layer thereof.
In a memory cell having the above structure as well, by applying a high voltage between the source region 105 and the source interconnection 116 according to the data to be written, the insulation in the silicon oxide film 114 is broken and the source region 105 and the source interconnection 116 are made conductive. Thus, data can be stored by conduction or nonconduction between the source region 105 and the source interconnection 116 in each memory cell.
On the other hand, U.S. Pat. No. 6,034,882 discloses a semiconductor nonvolatile memory device having a memory cell array and having a peripheral circuit shown in an equivalent circuit diagram of FIG. 4A.
Namely, as shown in FIG. 4A memory cells M are provided at intersecting points of conductive layers (C1, C3, C5, C7) receiving layer selection signals LSS by a switching transistor SWT controlled by a row decoder RD and conductive layers (C2, C4, C6) acting as the bit lines BL.
The above memory cell has a structure shown in for example FIG. 4B.
Namely, a p+ type polysilicon layer 202 is formed on a conductive layer 201 forming the conductive layers (C1, C3, C5, C7), and an n-type polysilicon layer 203 is formed at an upper layer thereof to thereby form a diode. A silicon oxide film 204 is formed at an upper layer of the polysilicon layer 203, an n+ type polysilicon layer 205 is formed at an upper layer thereof, and a conductive layer 206 forming the conductive layers (C2, C4, C6) is laid at an upper layer thereof.
Here, the polysilicon layer 203 and the polysilicon layer 205 are insulated by the silicon oxide film 204.
In a memory cell having the above structure, by applying a high voltage between the polysilicon layer 203 and the polysilicon layer 205 according to the data to be written, the insulation in the silicon oxide film 204 is broken and the polysilicon layer 203 and the polysilicon layer 205 are made conductive. Therefore, data can be stored according to existence/nonexistence of the diode element in each memory cell (portion where the polysilicon layer 202 and the polysilicon layer 203 are stacked).
In a memory cell having the structure shown in FIG. 1 to FIG. 3 described above, however, there was a problem in reproducibility and reliability of the breakage of insulation of the silicon oxide film.
Also, the semiconductor nonvolatile memory device shown in FIGS. 4A and 4B is configured by memory cells each comprised of a fuse of an insulating film breakage type and a diode as an active element connected therein repeating in three dimensions. Therefore, it becomes necessary to form a silicon layer having a crystallinity required for comprising the active element in an upper layer of the interconnection made of aluminum, so there is a large influence of heat treatment upon the aluminum interconnections and accompanying major difficulties in actual production.
Further, by stacking a plurality of layers having memory cells, for example, nine layers, it is possible to increase the degree of integration and to thereby realize a reduction of the manufacturing cost per unit storage capacity of the semiconductor nonvolatile memory device, but there was a problem in that, even if N number of layers are stacked, the manufacturing cost per unit storage capacity becomes larger than 1/N due to the influence of the peripheral circuits etc., so an effect of the reduction of cost cannot be sufficiently obtained.
An object of the present invention is to provide a semiconductor nonvolatile memory device capable of improving the reproducibility and reliability of the breakage of insulation of the silicon oxide film and capable of further reducing the manufacturing cost and a method for production of the same.
To attain the above object, a semiconductor nonvolatile memory device of the present invention has at least one memory cell and is programmable one time, wherein the memory cell comprises an impurity region of a first conductivity type formed in a semiconductor substrate, a first insulating film formed on the semiconductor substrate covering the impurity region, an opening formed in the first insulating film so as to reach the impurity region, and a program portion comprising a first semiconductor layer of the first conductivity type, a second insulating film, and a second semiconductor layer of a second conductivity type, the first semiconductor layer, the second insulating film and the second semiconductor layer being successively stacked in the opening, the first semiconductor layer being formed on the impurity region, the second insulating film being changed in a conductive state in response to a program data to thereby electrically connect between the first and second semiconductor layers.
In the semiconductor nonvolatile memory device of the present invention, preferably insulation breakage in the second insulating film in the program portion is caused by applying a predetermined voltage between the first semiconductor layer and the second semiconductor layer in response to the program data to be stored in the memory cell, and data is stored by the conduction or nonconduction between the first semiconductor layer and the second semiconductor layer in each memory cell.
In the semiconductor nonvolatile memory device of the present invention, preferably, in the memory cell, a gate electrode acting as a word line is formed on the semiconductor substrate via a gate insulating film, a channel forming region is provided on the semiconductor substrate below the gate electrode, a field-effect transistor using the impurity region as the drain region is formed, and the bit line is connected to the second semiconductor layer.
More preferably, the source region of the field-effect transistor is grounded.
Alternatively, more preferably, provision is further made of a means for detecting a current flowing from the source region of the field-effect transistor to the semiconductor substrate side.
Alternatively, more preferably, the word line and the bit line are connected to a row decoder and a column decoder including pass transistors for passing supplied signals therethrough, and more preferably, inverted signals of address signals are supplied to the row decoder and the column decoder from an external device together with forward signals.
In the semiconductor nonvolatile memory device of the present invention, preferably the plurality of memory cells are arranged in a matrix form.
In the semiconductor nonvolatile memory device of the present invention, the memory cell has an impurity region of a first conductivity type formed on the semiconductor substrate, a first insulating film formed on the semiconductor substrate while covering the impurity region, an opening formed in the first insulating film so as to reach the impurity region, and a first semiconductor layer of a first conductivity type, a second insulating film, and a second semiconductor layer of a second conductivity type successively stacked in the opening from the impurity region side.
By applying a predetermined voltage between the first semiconductor layer and the second semiconductor layer, the reproducibility and reliability are improved, and insulation breakage in the second insulating film can be caused.
Also, since a memory cell can be comprised by a simple structure, by making for example the row decoder and the column decoder by only pass transistors, the device can be produced while reducing the number of masks to about six, so the manufacturing cost can be suppressed.
Also, to attain the above object, a semiconductor nonvolatile memory device of the present invention has at least one memory cell and is programmable one time, wherein the memory cell comprises a first interconnection, a first insulating film formed on the first interconnection, an opening formed in the first insulating film so as to reach the first interconnection, a program portion comprising a first semiconductor layer of a first conductivity type, a second insulating film, and a second semiconductor layer of a second conductivity type, the first semiconductor layer, the second insulating film and the second semiconductor layer being successively stacked in the opening, the first semiconductor layer being formed on the first interconnection, the second insulating film being changed in a conductive state in response to a program data to thereby electrically connect between the first and second semiconductor layers, and a second interconnection formed connected to the second semiconductor layer.
In the semiconductor nonvolatile memory device of the present invention, preferably insulation breakage in the second insulating film in the program portion is caused by applying a predetermined voltage between the first semiconductor layer and the second semiconductor layer in response to the program data to be stored in the memory cell, and data is stored by the conduction or nonconduction between the first semiconductor layer and the second semiconductor layer in each memory cell.
In the semiconductor nonvolatile memory device of the present invention, preferably, in the memory cell, the first interconnection is a word line and the second interconnection is a bit line.
More preferably, the word line and the bit line are connected to a row decoder and a column decoder including pass transistors for passing supplied signals therethrough.
Also, more preferably, inverted signals of address signals are supplied to the row decoder and the column decoder from an external device together with the forward signals.
In the semiconductor nonvolatile memory device of the present invention, preferably the plurality of memory cells are arranged in a matrix form.
In the semiconductor nonvolatile memory device of the present invention, preferably a plurality of stacks of the first interconnection, first insulating film, and second interconnection are stacked while being insulated from each other, and in each stack, the plurality of memory cells are arranged in a matrix form so as to be connected to the first interconnection and the second interconnection.
In the semiconductor nonvolatile memory device of the present invention, the memory cell has the first interconnection, first insulating film formed on the first interconnection, opening formed in the first insulating film so as to reach the first interconnection, first semiconductor layer of a first conductivity type, second insulating film, and second semiconductor layer of a second conductivity type successively stacked in the opening from the first interconnection side, and the second interconnection formed connected to the second semiconductor layer.
By applying a predetermined voltage between the first semiconductor layer and the second semiconductor layer, the reproducibility and reliability are improved, and insulation breakage in the second insulating film can be caused.
Also, since the memory cell can be comprised by a simple structure, by making for example the row decoder and the column decoder by only pass transistors, the device can be produced while reducing the number of masks to about six, so the manufacturing cost can be suppressed.
Also, to attain the above object, a semiconductor nonvolatile memory device of the present invention has at least one memory cell and is programmable one time, wherein the memory cell comprises an impurity region of a first conductivity type formed in a first semiconductor layer on an insulating substrate, a first insulating film formed on the first semiconductor layer while covering the impurity region, an opening formed in the first insulating film so as to reach the impurity region, and a program portion comprising a second insulating film and a second semiconductor layer of a second conductivity type, the second insulating film and the second semiconductor layer being successively stacked in the opening, the second insulating film being formed on the impurity region, the second insulating film being changed in a conductive state in response to a program data to thereby electrically connect between the impurity region and the second semiconductor layer.
In the semiconductor nonvolatile memory device of the present invention, preferably the insulation breakage in the second insulating film in the program portion is caused by applying a predetermined voltage between the impurity region and the second semiconductor layer in response to the program data to be stored in the memory cell, and data is stored by the conduction or nonconduction between the impurity region and the second semiconductor layer in each memory cell.
In the semiconductor nonvolatile memory device of the present invention, preferably, in the memory cell, a gate electrode forming the word line is formed on the first semiconductor layer via a gate insulating film, a channel forming region is provided in the first semiconductor layer below the gate electrode, a field-effect transistor is formed using the impurity region as the drain region, and a bit line is connected to the second semiconductor layer.
More preferably the source region of the field-effect transistor is grounded.
Alternatively, more preferably, provision is further made of a means for detecting a current flowing from the source region of the field-effect transistor to the semiconductor substrate side.
Alternatively, more preferably, the word line and the bit line are connected to a row decoder and a column decoder including pass transistors for passing supplied signals therethrough, and more preferably, inverted signals of address signals are supplied to the row decoder and the column decoder from an external device together with forward signals.
In the semiconductor nonvolatile memory device of the present invention, preferably the plurality of memory cells are arranged in the matrix form.
In the semiconductor nonvolatile memory device of the present invention, preferably a plurality of the first semiconductor layers are stacked while being insulated from each other, and the memory cells are arranged in a matrix form in each of the first semiconductor layers.
In the semiconductor nonvolatile memory device of the present invention, the memory cell has an impurity region of a first conductivity type formed in the first semiconductor layer on the insulating substrate, a first insulating film formed on the first semiconductor layer while covering the impurity region, an opening formed in the first insulating film so as to reach the impurity region, and a second insulating film and second semiconductor layer of a second conductivity type successively stacked in the opening from the impurity region side.
By applying a predetermined voltage between the impurity region in the first semiconductor layer having an SOI (semiconductor on insulator) structure and the second semiconductor layer, the reproducibility and reliability can be improved in causing insulation breakage in the second insulating film.
Also, since the memory cell can be comprised by a simple structure, by making for example the row decoder and the column decoder by only pass transistors, the device can be produced while reducing the number of masks to about six, so the manufacturing cost can be suppressed.
To attain the above object, a method for production of a semiconductor nonvolatile memory device of the present invention is a method for production of a semiconductor nonvolatile memory device having at least one memory cell and programmable one time, wherein a process of forming the memory cell includes steps of forming an impurity region of a first conductivity type in a semiconductor substrate, forming a first insulating film on the semiconductor substrate while covering the impurity region, forming an opening in the first insulating film so as to reach the impurity region, forming a first semiconductor layer of a first conductivity type on the impurity region in the opening, forming a second insulating film on the first semiconductor layer in the opening, and forming a second semiconductor layer of a second conductivity type on the second insulating film in the opening.
In the method for production of a semiconductor nonvolatile memory device of the present invention, preferably the step of forming the first semiconductor layer is a step of forming the same by selective epitaxial growth.
In the method for production of a semiconductor nonvolatile memory device of the present invention, preferably a step of forming a gate electrode acting as a word line on the semiconductor substrate acting as a channel forming region via a gate insulating film is provided before the step of forming the impurity region of the first conductivity type on the semiconductor substrate, and in the step of forming the impurity region of the first conductivity type on the semiconductor substrate, in the semiconductor substrate on both side portions of the gate electrode a source region and a drain region acting as the impurity region are formed, and provision is further made of a step of forming a bit line at an upper layer of the second semiconductor layer.
More preferably, the row decoder and the column decoder connected to the word line and the bit line are formed by only pass transistors.
In the method for production of the semiconductor nonvolatile memory device of the present invention, when forming memory cells arranged in a matrix form or the like, the impurity region of the first conductivity type is formed on the semiconductor substrate, the first insulating film is formed on the semiconductor substrate while covering the impurity region, and the opening is formed in the first insulating film so as to reach the impurity region. Next, in the opening, the first semiconductor layer of the first conductivity type is formed on the impurity region, the second insulating film is formed on the first semiconductor layer, and further the second semiconductor layer of the second conductivity type is formed on the second insulating film.
According to the method for production of a semiconductor nonvolatile memory device of the present invention, it is possible to produce a semiconductor nonvolatile memory device having memory cells capable of improving reproducibility and reliability in causing insulation breakage in a second insulating film by applying a predetermined voltage between the first semiconductor layer and the second semiconductor layer, For example, by making for example the row decoder and the column decoder by only pass transistors, it is possible to produce the device while reducing the number of masks to about six and to suppress the manufacturing cost.
To attain the above object, a method for production of a semiconductor nonvolatile memory device of the present invention is a method for production of a semiconductor nonvolatile memory device having at least one memory cell and programmable one time, wherein a process of forming the memory cell includes steps of forming a first insulating film at an upper layer of a first interconnection, forming an opening in the first insulating film so as to reach the first interconnection, forming a first semiconductor layer of a first conductivity type on the first interconnection in the opening, forming a second insulating film on the first semiconductor layer in the opening, forming a second semiconductor layer of a second conductivity type on the second insulating film in the opening, and forming a second interconnection so as to be connected to the second semiconductor layer.
In the method for production of a semiconductor nonvolatile memory device of the present invention, preferably the first interconnection is formed as a word line, and the second interconnection is formed as a bit line.
More preferably, the row decoder and the column decoder connected to the word line and the bit line are formed by only pass transistors.
In the method for production of a semiconductor nonvolatile memory device of the present invention, when forming memory cells arranged in a matrix form, the first insulating film is formed at an upper layer of the first interconnection, the opening is opened in the first insulating film so as to reach the first interconnection, the first semiconductor layer of the first conductivity type is formed on the first interconnection in the opening, the second insulating film is formed on the first semiconductor layer, and further the second semiconductor layer of the second conductivity type is formed on the second insulating film. Next, the second interconnection is formed so as to be connected to the second semiconductor layer.
According to the method for production of a semiconductor nonvolatile memory device of the present invention, it is possible to produce a semiconductor nonvolatile memory device having memory cells capable of improving reproducibility and reliability in causing insulation breakage in a second insulating film by applying a predetermined voltage between the first semiconductor layer and the second semiconductor layer. For example, by making the row decoder and the column decoder by only pass transistors, it is possible to produce the device while reducing the number of masks to about six and to suppress the manufacturing cost.
To attain the above object, a method for production of a semiconductor nonvolatile memory device of the present invention is a method for production of a semiconductor nonvolatile memory device having at least one memory cell and programmable one time, wherein a process of forming the memory cell includes steps of forming an impurity region of a first conductivity type in a first semiconductor layer on an insulating substrate, forming a first insulating film on the first semiconductor layer while covering the impurity region, forming an opening in the first insulating film so as to reach the impurity region, forming a second insulating film on the impurity region in the opening, and forming a second semiconductor layer of a second conductivity type on the second insulating film in the opening.
In the method for production of the semiconductor nonvolatile memory device of the present invention, preferably a step of forming a gate electrode acting as a word line on the first semiconductor layer acting as a channel forming region via a gate insulating film is provided before the step of forming the impurity region of the first conductivity type in the first semiconductor layer, and in the step of forming the impurity region of the first conductivity type in the first semiconductor layer, in the first semiconductor layer on both side portions of the gate electrode a source region and a drain region acting as the impurity region are formed, and provision is further made of a step of forming a bit line at an upper layer of the second semiconductor layer.
More preferably the row decoder and the column decoder connected to the word line and the bit line are formed by only pass transistors.
In the method for production of the semiconductor nonvolatile memory device of the present invention, when forming memory cells arranged in a matrix form or the like, the impurity region of the first conductivity type is formed in the first semiconductor layer on the insulating substrate, the first insulating film is formed on the first semiconductor layer while covering the impurity region, and the opening is formed in the first insulating film so as to reach the impurity region. Next, in the opening, the second insulating film is formed on the impurity region, and the second semiconductor layer of the second conductivity type is formed on the second insulating film.
According to the method for production of a semiconductor nonvolatile memory device of the present invention, it is possible to produce a semiconductor nonvolatile memory device having memory cells capable of improving reproducibility and reliability in causing insulation breakage in a second insulating film by applying a predetermined voltage between the impurity region and the second semiconductor layer. By making for example the row decoder and the column decoder by only pass transistors, it is possible to produce the device while reducing the number of masks to about six and suppress the manufacturing cost.